In the extremely unlikely event that games are able to be played in the UK at some point relatively soon, but France and Canada have restrictions, then Catalans and Toronto will have to just play their "home" games over here. I'm booked for Toronto away in July and don't for one second expect to be going, and nor do I really expect any professional rugby league game to be played in 2020. At least not with a crowd. The only way I see it as even marginally possible is if there's a significantly shortened season played out much later in the year, that then enables a top four (1 V 4, 2 V 3, Grand Final) play off series to be held once crowds are able to return.

No Challenge Cup games or internationals.

If there is any club Rugby League played in this country in 2020, I'll eat my proverbial hat.

So with Leeds games in hand and superior points difference will they be crowned as champions ?

No

A double whammy if your a united fan as well

It's a little different f0r Leeds United, as the bulk of the football season has been played, although, unlike Liverpool in the Premiership, Leeds ,although top, would not be certainties to remain there if/when all games are complete (should that ever happen).
The RL season is still in it's infancy, with Leeds having completed just 5 games out of 29 and they're not even top of the pile, albeit with a couple of games in hand.

Not sure when it becomes "fair" to award a title for an incomplete season but, 80/85% would be a reasonable line, 15% (approx.) is not. Dont blame him for trying though.